Quantitative electrochemical detection of cathepsin B activity in breast cancer cell lysates using carbon nanofiber nanoelectrode arrays toward identification of cancer formation

Electrochemical biosensors for early detection of breast cancer

Breast cancer continues to be a significant contributor to global cancer deaths, particularly among women. This highlights the critical role of early detection and treatment in boosting survival rates. While conventional diagnostic methods like mammograms, biopsies, ultrasounds, and MRIs are valuable tools, limitations exist in terms of cost, invasiveness, and the requirement for specialized equipment and trained personnel. Recent shifts towards biosensor technologies offer a promising alternative for monitoring biological processes and providing accurate health diagnostics in a cost-effective, non-invasive manner. These biosensors are particularly advantageous for early detection of primary tumors, metastases, and recurrent diseases, contributing to more effective breast cancer management. The integration of biosensor technology into medical devices has led to the development of low-cost, adaptable, and efficient diagnostic tools. In this framework, electrochemical screening platforms have garnered significant attention due to their selectivity, affordability, and ease of result interpretation. The current review discusses various breast cancer biomarkers and the potential of electrochemical biosensors to revolutionize early cancer detection, making provision for new diagnostic platforms and personalized healthcare solutions.

Identification and Validation of Serum CST1 as a Diagnostic Marker for Differentiating Early-Stage Non-Small Cell Lung Cancer from Pulmonary Benign Nodules

Background

Effective means for early diagnosis are imperative to reduce death rate of non-small cell lung cancer (NSCLC) patients. We aimed to find out high-performance serologic markers to distinguish early-stage NSCLC patients from benign pulmonary nodule patients and healthy controls (HC). Cystatin-SN (CST1) is an active cysteine protease inhibitor of the CST superfamily, involving in the processes of inflammation and tumorigenesis. This is the first exploration of the diagnostic and prognostic values of serum CST1 in NSCLC.

Methods

We analyzed the transcriptome data from The Cancer Genome Atlas and the Gene Expression Omnibus database, screened biomarkers for NSCLC, and verified the candidate markers via the ONCOMINE database. Then, we performed ELISA, western blotting, and immunohistochemistry analysis to detect the expression levels of CST1 in NSCLC cell lines, tumor tissues, and serum samples of clinical cohorts.

Results

We identified 3 up-regulated secreted protein-encoding genes, validated the expression levels of CST1 in NSCLC tumor tissues and cell lines, and found that serum CST1 levels of NSCLC (4289 ± 2405 pg/mL) were significantly higher than those of PBN patients (1558 ± 441 pg/mL, P < .0001) and healthy controls (1529 ± 416 pg/mL, P < .0001). The AUC of the combination of CST1, Cytokeratin 19 fragment (Cyfra21-1), and Carcinoembryonic antigen (CEA) for distinguishing early-stage NSCLC from PBN/HC was as high as .914/0.925. Furthermore, our results suggested that the NSCLC patient with low serum CST1 level had a better survival rate.

Conclusions

Serum CST1 may serve as a novel diagnostic marker for differentiating early-stage NSCLC from PBN and HC, and could be used as a prognosis predictor in NSCLC patients.

Quantitative Detection of Cathepsin B Activity in Neutral pH Buffers Using Gold Microelectrode Arrays: Toward Direct Multiplex Analyses of Extracellular Proteases in Human Serum

Proteases are critical signaling molecules and prognostic biomarkers for many diseases including cancer. There is a strong demand for multiplex bioanalytical techniques that can rapidly detect the activity of extracellular proteases with high sensitivity and specificity. This study demonstrates an activity-based electrochemical biosensor of a 3 × 3 gold microelectrode array for the detection of cathepsin B activity in human serum diluted in a neutral buffer. Proteolysis of ferrocene-labeled peptide substrates functionalized on 200 × 200 μm microelectrodes is measured simultaneously over the nine channels by AC voltammetry. The protease activity is represented by the inverse of the exponential decay time constant (1/τ), which equals to (k_cat/K_M)[CB] based on the Michaelis-Menten model. An enhanced activity of the recombinant human cathepsin B (rhCB) is observed in a low-ionic-strength phosphate buffer at pH = 7.4, giving a very low limit of detection of 8.49 × 10^-4 s^-1 for activity and 57.1 pM for the active rhCB concentration that is comparable to affinity-based enzyme-linked immunosorbent assay (ELISA). The cathepsin B presented in the human serum sample is validated by ELISA, which mainly detects the inactive proenzyme, while the electrochemical biosensor specifically measures the active cathepsin B and shows significantly higher decay rates when rhCB and human serum are activated. Analyses of the kinetic electrochemical measurements with spiked active cathepsin B in human serum provide further assessment of the protease activity in the complex sample. This study lays the foundation to develop the gold microelectrode array into a multiplex biosensor for rapid detection of the activity of extracellular proteases toward cancer diagnosis and treatment assessment.

PNA-Guided Peptide Engineering of Aptamer Sensor for Protease-Unlocked Molecular Imaging

Protease-triggered control of functional DNA has remained unachieved, leaving a significant gap in activatable DNA biotechnology. Here we disclose the design of a protease-activatable aptamer technology that can perform molecular sensing and imaging function in a tumor-specific manner. The system is constructed by locking structure-switching activity of aptamer using a rationally designed PNA-peptide-PNA triblock copolymer. Highly selective cleavage of the peptide substrate is achieved by protease-mediated enzymatic reaction that result in reduced binding affinity of PNA to the aptamer module, with the subsequently recovering its biosensing function. We demonstrated that the DNA/peptide/PNA hybrid system not only allows for tumor cell-selective ATP imaging in vitro , but it also produce a fluorescent signal in vivo with improved tumor specificity. This work illustrates the potential of bridging the gap between functional DNA field and peptide area for precise biomedical applications.

Considerations for the discovery and development of 3-chymotrypsin-like cysteine protease inhibitors targeting SARS-CoV-2 infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the COVID-19 pandemic. The coronavirus 3-chymotrypsin-like protease (3CLpro) controls virus replication and is therefore considered a major target and promising opportunity for rational-based antiviral discovery with direct acting agents. Here we review first-generation SARS-CoV-2 3CLpro inhibitors PF-07304814, GC-376, and CDI-45205 that are being delivered either by injection or inhalation due to their low intrinsic oral bioavailability. In addition, PF-07321332 is now emerging as a promising second-generation clinical candidate for oral delivery. A key challenge to the development of novel 3CLpro inhibitors is the poor understanding of the predictive value of in vitro potency toward clinical efficacy, an issue complicated by the involvement of host proteases in virus entry. Further preclinical and clinical validation will be key to establishing 3CLpro inhibitors as a bona fide class for future SARS-CoV-2 therapeutics for both hospitalized and outpatient populations.

Electrospun Carbon Nanofibers from Biomass and Biomass Blends-Current Trends

In recent years, ecological issues have led to the search for new green materials from biomass as precursors for producing carbon materials (CNFs). Such green materials are more attractive than traditional petroleum-based materials, which are environmentally harmful and non-biodegradable. Biomass could be ideal precursors for nanofibers since they stem from renewable sources and are low-cost. Recently, many authors have focused intensively on nanofibers' production from biomass using microwave-assisted pyrolysis, hydrothermal treatment, ultrasonication method, but only a few on electrospinning methods. Moreover, still few studies deal with the production of electrospun carbon nanofibers from biomass. This review focuses on the new developments and trends of electrospun carbon nanofibers from biomass and aims to fill this research gap. The review is focusing on recollecting the most recent investigations about the preparation of carbon nanofiber from biomass and biopolymers as precursors using electrospinning as the manufacturing method, and the most important applications, such as energy storage that include fuel cells, electrochemical batteries and supercapacitors, as well as wastewater treatment, CO2 capture, and medicine.

A comprehensive review summarizing the recent biomedical applications of functionalized carbon nanofibers

Since the discovery and fabrication of carbon nanofibers (CNFs) over a decade ago, scientists foster to discover novel myriad potential applications for this material in both biomedicine and industry. The unique economic viability, mechanical, electrical, optical, thermal, and structural properties of CNFs led to their rapid emergence. CNFs become an artificial intelligence platform for different uses, including a wide range of biomedical applications. Furthermore, CNFs have exceptionally large surface areas that make them flexible for tailoring and functionalization on demand. This review highlights the recent progress and achievements of CNFs in a wide range of biomedical fields, including cancer therapy, biosensing, tissue engineering, and wound dressing. Besides the synthetic techniques of CNFs, their potential toxicity and limitations, as biomaterials in real clinical settings, will be presented. This review discusses CNF's future investigations in other biomedical fields, including gene delivery and bioimaging and CNFs risk assessment.

Dual inhibition of SARS-CoV-2 and human rhinovirus with protease inhibitors in clinical development

The 3-chymotrypsin-like cysteine protease (3CLpro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is considered a major target for the discovery of direct antiviral agents. We previously reported the evaluation of SARS-CoV-2 3CLpro inhibitors in a novel self-assembled monolayer desorption ionization mass spectrometry (SAMDI-MS) enzymatic assay (Gurard-Levin et al., 2020). The assay was further improved by adding the rhinovirus HRV3C protease to the same well as the SARS-CoV-2 3CLpro enzyme. High substrate specificity for each enzyme allowed the proteases to be combined in a single assay reaction without interfering with their individual activities. This novel duplex assay was used to profile a diverse set of reference protease inhibitors. The protease inhibitors were grouped into three categories based on their relative potency against 3CLpro and HRV3C including those that are: equipotent against 3CLpro and HRV3C (GC376 and calpain inhibitor II), selective for 3CLpro (PF-00835231, calpain inhibitor XII, boceprevir), and selective for HRV3C (rupintrivir). Structural analysis showed that the combination of minimal interactions, conformational flexibility, and limited bulk allows GC376 and calpain inhibitor II to potently inhibit both enzymes. In contrast, bulkier compounds interacting more tightly with pockets P2, P3, and P4 due to optimization for a specific target display a more selective inhibition profile. Consistently, the most selective viral protease inhibitors were relatively weak inhibitors of human cathepsin L. Taken together, these results can guide the design of cysteine protease inhibitors that are either virus-specific or retain a broad antiviral spectrum against coronaviruses and rhinoviruses.

Nanoneedle-Based Materials for Intracellular Studies

Nanoneedles, defined as high aspect ratio structures with tip diameters of 5 to approximately 500 nm, are uniquely able to interface with the interior of living cells. Their nanoscale dimensions mean that they are able to penetrate the plasma membrane with minimal disruption of normal cellular functions, allowing researchers to probe the intracellular space and deliver or extract material from individual cells. In the last decade, a variety of strategies have been developed using nanoneedles, either singly or as arrays, to investigate the biology of cancer cells in vitro and in vivo. These include hollow nanoneedles for soluble probe delivery, nanocapillaries for single-cell biopsy, nano-AFM for direct physical measurements of cytosolic proteins, and a wide range of fluorescent and electrochemical nanosensors for analyte detection. Nanofabrication has improved to the point that nanobiosensors can detect individual vesicles inside the cytoplasm, delineate tumor margins based on intracellular enzyme activity, and measure changes in cell metabolism almost in real time. While most of these applications are currently in the proof-of-concept stage, nanoneedle technology is poised to offer cancer biologists a powerful new set of tools for probing cells with unprecedented spatial and temporal resolution.

Integration of a peptide–DNA conjugate with multiple cyclic signal amplification for the ultrasensitive detection of cathepsin B activity

We integrate a peptide–DNA conjugate with multiple cyclic signal amplification for the sensitive detection of cathepsin B activity.

Synthesis and preliminary radiopharmacological characterisation of an 11 C-labelled azadipeptide nitrile as potential PET tracer for imaging of cysteine cathepsins

An O-methyltyrosine-containing azadipeptide nitrile was synthesised and investigated for its inhibitory activity towards cathepsins L, S, K, and B. Labelling with carbon-11 was accomplished by reaction of the corresponding phenolic precursor with [¹¹ C]methyl iodide starting from cyclotron-produced [¹¹ C]methane. Radiopharmacological evaluation of the resulting radiotracer in a mouse xenograft model derived from a mammary tumour cell line by small animal PET imaging indicates tumour targeting with complex pharmacokinetics. Radiotracer uptake in the tumour region was considerably lower under treatment with the nonradioactive reference compound and the epoxide-based irreversible cysteine cathepsin inhibitor E64. The in vivo behaviour observed for this radiotracer largely confirms that of the corresponding ¹⁸ F-fluoroethylated analogue and suggests the limited suitability of azadipeptide nitriles for the imaging of tumour-associated cysteine cathepsins despite target-mediated uptake is evidenced.

Electrochemical Activity Assay for Protease Analysis Using Carbon Nanofiber Nanoelectrode Arrays

There is a strong demand for bioanalytical techniques to rapidly detect protease activities with high sensitivity and high specificity. This study reports an activity-based electrochemical method toward this goal. Nanoelectrode arrays (NEAs) fabricated with embedded vertically aligned carbon nanofibers (VACNFs) are functionalized with specific peptide substrates containing a ferrocene (Fc) tag. The kinetic proteolysis curves are measured with continuously repeated ac voltammetry, from which the catalytic activity is derived as the inverse of the exponential decay time constant based on a heterogeneous Michaelis-Menten model. Comparison of three peptide substrates with different lengths reveals that the hexapeptide H2N-(CH2)4-CO-Pro-Leu-Arg-Phe-Gly-Ala-NH-CH2-Fc is the optimal probe for cathepsin B. The activity strongly depends on temperature and is the highest around the body temperature. With the optimized peptide substrate and measuring conditions, the limit of detection of cathepsin B activity and concentration can reach 2.49 × 10-4 s-1 and 0.32 nM, respectively. The peptide substrates show high specificity to the cognate proteases, with negligible cross-reactions among three cancer-related proteases cathepsin B, ADAM10, and ADAM17. This electrochemical method can be developed into multiplex chips for rapid profiling of protease activities in cancer diagnosis and treatment monitoring.

Research progresses on the functional polypeptides in the detection and imaging of breast cancer

Polypeptides as functional groups continue to garner significant interest in the detection and imaging of breast cancer, working as recognition elements, signal sources, building blocks and therapeutic reagents, etc.

Recent advances in carbon based nanosystems for cancer theranostics

This review deals with four different types of carbon allotrope based nanosystems and summarizes the results of recent studies that are likely to have applications in cancer theranostics. We discuss the applications of these nanosystems for cancer imaging, drug delivery, hyperthermia, and PDT/TA/PA.

Biosensors for breast cancer diagnosis: A review of bioreceptors, biotransducers and signal amplification strategies

Breast cancer is highly prevalent in females and accounts for second highest number of deaths, worldwide. Cumbersome, expensive and time consuming detection techniques presently available for detection of breast cancer potentiates the need for development of novel, specific and ultrasensitive devices. Biosensors are the promising and selective detection devices which hold immense potential as point of care (POC) tools. Present review comprehensively scrutinizes various breast cancer biosensors developed so far and their technical evaluation with respect to efficiency and potency of selected bioreceptors and biotransducers. Use of glycoproteins, DNA biomarkers, micro-RNA, circulatory tumor cells (CTC) and some potential biomarkers are introduced briefly. The review also discusses various strategies used in signal amplification such as nanomaterials, redox mediators, p19 protein, duplex specific nucleases (DSN) and redox cycling.

Towards the electrochemical diagnosis of cancer: nanomaterial-based immunosensors and cytosensors

In this review, nanomaterial based electrochemical biosensors including electrochemical immunosensors and cytosensors towards cancer detection are covered.